Indications for NIRS

Indications for Two Site NIRS Monitoring in the Pediatric Cardiac Patient Undergoing Non-cardiac Surgery.

Suanne M. Daves, MD, Medical Director, Pediatric Cardiac Anesthesia

Perioperative Cardiac Arrest

Perioperative cardiac arrest is ten times more likely to occur in infants with congenital heart disease¹. In the child without cardiac disease, arrest is often the result of global asphyxia from respiratory failure. In contrast, the child with congenital heart disease is more likely to arrest as the result of pulmonary steal in single ventricle physiology, an arrhythmia, a coronary event, an aortopulmonary shunt occlusion, or a pulmonary hypertensive crisis.

Cardiac arrest has at least four phases:

· The phase prior to the arrest

· The phase of no-flow (prior to compressions)

· The phase of low-flow (during compressions)

· The recovery phase.

The Phases of Cardiac Arrest

In the cardiac population, the phase prior to arrest may represent the greatest opportunity to intervene and prevent pulseless arrest. Much of our attention has focused on the no- and low-flow phases with improvements in rapid response, the assessment of adequate compressions, and protocols for access and drug delivery. However, recent advances in the early assessment of low cardiac output syndrome (LCOS) by adding near infrared spectroscopy (NIRS) to conventional monitoring modalities may allow clinicians recognize evolving shock, manage resuscitation promptly, and potentially prevent cardiac arrest².

Multi-Site NIRS Monitoring

Mixed venous saturation (MvO₂) has been validated as an accurate global assessment of oxygen economy. In children with intracardiac shunts, samples obtained from the distal pulmonary artery will not reflect a true mixed venous sample. However, samples from the distal SVC are widely accepted as an accurate surrogate³. Non-invasive tissue oximetry is the non-invasive measurement of the average of oxygenated hemoglobin in a ‘region’ of the body. The majority of blood in these fields is venous and therefore correlates with MvO₂. This technology is well-studied and has been validated against a variety of invasive measurements. Normal 0 false false false EN-US X-NONE X-NONE For two site monitoring, sensors are typically placed on the forehead (cerebral NIRS) and the renal bed (somatic NIRS). Somatic NIRS may be the earliest indication of evolving shock or LCOS since tissue beds with strong autoregulatory control may maintain adequate oxygen delivery until very late. Two site monitoring may identify evolving LCOS at the very early stages, prior to rising lactate levels, deteriorating acid-base levels, low urine output, or gastric tonometry.

Indications for Two Site NIRS Monitoring for Cardiac Patients Undergoing Non-Cardiac Procedures/Surgery

· Patients with single ventricle physiology

· Patients with partial (Glenn) or total (Fontan) cavopulmonary circulation

· Patients with pulmonary hypertension

· Patients with Williams Syndrome or non-syndromic supravalvar aortic stenosis (SVAS)

· Patients with biventricular physiology and mitral or aortic valve disease

· Patients with ventricular dysfunction (moderate to severe)

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